Weather Compensation on Both Rads and UFH?

[GeorgeWBush]

Hi,

We have just extended our house and are coming to doing the plumbing throughout the house. We shall be laying all new pipework, rads etc. Old part of the house is solid wall (1930s) and the extended part is cavity wall.

I would like to have a mixture of radiators and UFH with zones as follows:
Zone 1 Radiators - upstairs 4 beds, bath and landing
Zone 2 radiators - Downstairs, 1/2 hallway, reception room, shower/wc room
Zone 3 UFH - Kitchen
Zone 4 UFH - 1/2 Hallway and living room
Zone 5 Cylinder (not sure if this is sep zone?)

I would like to have an unvented setup, most likely the ACV Smartline 210 litre and a Vaillant Ecotec Plus 630 System boiler. Controls will most likely be Honeywell.

My questions is, Can this all be setup with the Vaillant weather compensation control? i.e. Can the weather compensation be used to control both the radiators and the ufh?

Thanks for looking.

 

[Agile]

Have you chosen the 630 after doing a whole house heat loss calculation? If not then on what basis have you chosen it?

Are the new cavity walls insulated as one would expect them to be?

You dont mention the UFH floor construction. Are they solid with at least 80mm of insulation below concrete?

You seem to want to design a significant heating system without professional on site asssistance.

Tony

 

[D_Hailsham]

I would like to have a mixture of radiators and UFH with zones as follows:
Zone 1: Radiators - upstairs 4 beds, bath and landing
Zone 2: Radiators - Downstairs, 1/2 hallway, reception room, shower/wc room
Zone 3: UFH - Kitchen
Zone 4: UFH - 1/2 Hallway and living room

Do you really want to be able to control the times and temperature of each of these zones separately? If not, you are complicating things unnecessarily.

Zone 5: Cylinder (not sure if this is sep zone?)

Yes, it is a separate zone as it has its own time and temperature control.

Vaillant Ecotec Plus 630 System boiler.

How did you arrive at the size of boiler required? Did you use the Whole House Boiler Size Calculator?. If not, you should do so.

Controls will most likely be Honeywell.

My questions is,[/b] Can this all be setup with the Vaillant weather compensation control? i.e. Can the weather compensation be used to control both the radiators and the ufh?

If you are using Vaillant WC controls, why do you think there is a need for Honeywell controls as well?

ACV Smartline 210 litre

Why have you chosen this one?

 

[GeorgeWBush]

Have you chosen the 630 after doing a whole house heat loss calculation?

I've run through a boiler sizing tool online and it calculated i needed a 25KW boiler.

If not then on what basis have you chosen it?

Plumber advised this boiler

Are the new cavity walls insulated as one would expect them to be?

Yes, 100mm dritherm.

You dont mention the UFH floor construction. Are they solid with at least 80mm of insulation below concrete?

Construction will be 100mm celotex, 55mm liquid/latex type screed.

You seem to want to design a significant heating system without professional on site asssistance.Tony

I do have a plumber but he is not knowledgeable on weather compensation so I would like to re-search myself before discussing further with him.

 

[GeorgeWBush]

I would like to have a mixture of radiators and UFH with zones as follows:
Zone 1: Radiators - upstairs 4 beds, bath and landing
Zone 2: Radiators - Downstairs, 1/2 hallway, reception room, shower/wc room
Zone 3: UFH - Kitchen
Zone 4: UFH - 1/2 Hallway and living room

Do you really want to be able to control the times and temperature of each of these zones separately? If not, you are complicating things unnecessarily.

I thought I would be able to save gas by doing this. Is this OTT? What would you advise?

Vaillant Ecotec Plus 630 System boiler.

How did you arrive at the size of boiler required? Did you use the Whole House Boiler Size Calculator?. If not, you should do so.

I've run through a boiler sizing tool online and it calculated i needed a 25KW boiler. Plumber advised the Ecotec 630 boiler.

Controls will most likely be Honeywell.

My questions is,[/b] Can this all be setup with the Vaillant weather compensation control? i.e. Can the weather compensation be used to control both the radiators and the ufh?

If you are using Vaillant WC controls, why do you think there is a need for Honeywell controls as well?

In addition to the Weather Controller, I thought we would need a programmable thermostat for each zone.

ACV Smartline 210 litre

Why have you chosen this one?

Based on reviews it looks to be the best performing cylinder available (especially in terms of reheat times).

 

[ALEC1]

you are right to want weather compensation and the acv cylinder...but wrong to choose honeywell controls as the honeywell controls that allow weather compensation are not available in the UK

You can use vaillant controls, but it is very specialised.

its a much better bet to use a viessmann boiler and their own brass bodied mixing valve and actuator...

they really are fantastic bits of kit!

again it is very specialised, so good luck!

 

[Agile]

I would be surprised if you really need 25 kW.

In any case the sizing assumes all zones are being heated at the same time. Hopefully you will set your controls accordingle.

Furthermore, most programs will ignore the fact that you have better than expected insulation in your floors.

I suggest you use the whole house method as linked to by David as we find that gives very consistant results.

I would be VERY surprised if a 24 kW boiler would not be totally adequate. Oversizing a boiler creates many problems and can reduce efficiency. This is particularly so with many zones when they are properly timed/controlled as the load on the boiler at any time can well be below its minimum output power and then it can only modulate by cycling on/off which is inefficient.

Reheat times seem very important to many people but if used properly they should not be. I would prefer a larger cylinder with a lower reheat time for myself.

You have not said how many people live there and what their water usage is. You only mention one bathroom and it could be that 210 li is totally adequate.

Tony Glazier

 

[ALEC1]

Tony, you are misunderstanding how the vaillant and viessmann weather compensation works!

how many have you installed and what is your experience with the?

 

[Agile]

I never mentioned weather compensation!

When Alex is about its like mentioning the war to a German!

 

[ALEC1]

thats what the thread is about tony!

read the title!

Over sizing is less of an issue with weather compensation, but clearly stupid...the real issues are about the installers understanding the system design and control implications so that the end user can benefit from decent economical and reliable heating system!

 

[GeorgeWBush]

I would be surprised if you really need 25 kW.

In any case the sizing assumes all zones are being heated at the same time. Hopefully you will set your controls accordingle.

Furthermore, most programs will ignore the fact that you have better than expected insulation in your floors.

I suggest you use the whole house method as linked to by David as we find that gives very consistant results.

I would be VERY surprised if a 24 kW boiler would not be totally adequate. Oversizing a boiler creates many problems and can reduce efficiency. This is particularly so with many zones when they are properly timed/controlled as the load on the boiler at any time can well be below its minimum output power and then it can only modulate by cycling on/off which is inefficient.

Reheat times seem very important to many people but if used properly they should not be. I would prefer a larger cylinder with a lower reheat time for myself.

You have not said how many people live there and what their water usage is. You only mention one bathroom and it could be that 210 li is totally adequate.

Tony Glazier

Thanks Tony for your views. I've ran the program linked to above (thanks D_Hailsham!) and it has advised I need 23.44 KW. It's a lot lower than what I has previously been advised, is this a good approximation?

With regards to the ACV 210 Litre, I was previously looking at the OSO Super S 250 litre, but I couldn't find performance figures in the format that are available on the ACV cylinder (litres in the first 10 minutes, litres perhour at various temps etc) so it was very difficult to compare the 2 directly. The ACV has some very impressive performance figures hence my picking it - 406 litres at 40C in the first 10 minutes, continuous flow at 40C of 1132litres/min.

We have 6 living in our house, 3 adults, 3 kids (3-9 years old). We all use the bath in the morning in a 1 hour timeslot, which involves 3 showers tops. A couple of showers in the evening and generally the occasional bath during the week. A couple of evenings a week will involve the kids having baths one after another (3 sometimes 4 on the trot). We will be having a washing machine + dishwasher.

 

[GeorgeWBush]

you are right to want weather compensation and the acv cylinder...but wrong to choose honeywell controls as the honeywell controls that allow weather compensation are not available in the UK

You can use vaillant controls, but it is very specialised.

its a much better bet to use a viessmann boiler and their own brass bodied mixing valve and actuator...

they really are fantastic bits of kit!

again it is very specialised, so good luck!

Hi Alec, thanks for the advice. I've read about Viessman and they do seem to be very highly regarded by a lot of people. Unfortuately in our area it's pretty much unheard of. I was worried about going for Viessman and then finding when something went wrong that local plumbers knew nothing about them. Hence going for Vaillant, more plumbers are knowledgeable about Vaillant.

With regards to the Honeywell Controlls not integrating with the Vaillant weather compensator, no problem, I'll go with Vaillant controls throughout.

Would both the Vaillant and Viessman weather compensator (WC) controls provide Weather Compensation on both the UFH and Rads at the same time?

Is it even worth getting WC on UFH?

Thanks.

 

[Agile]

With regards to the ACV 210 Litre, I was previously looking at the OSO Super S 250 litre, but I couldn't find performance figures in the format that are available on the ACV cylinder (litres in the first 10 minutes, litres perhour at various temps etc) so it was very difficult to compare the 2 directly. The ACV has some very impressive performance figures hence my picking it - 406 litres at 40C in the first 10 minutes, continuous flow at 40C of 1132litres/min.

We have 6 living in our house, 3 adults, 3 kids (3-9 years old). We all use the bath in the morning in a 1 hour timeslot, which involves 3 showers tops.

I calculate a flow of 1132 li/min will need a 3000 kW boiler!

With six adults I strongly recommend a 300 li cylinder! I also think that you are misinterpreting the cylinder figures.

As I suggested 24 kW is likely to be totally adequate when the system is properly configured and used with a 300 li cylinder.

WC still cannot make a boiler give less that its rated minimum output power which is why oversizing a boiler is problematic.

There is also another problem with the settings of WC as they would ideally need different settings for the solid wall parts compared with the new well insulated parts. Nevertheless, properly installed and set up it should still work well.

Tony

 

[GeorgeWBush]

1132litres/min.

OOPS, i meant of course 1132 litres/hour, not per minute!

 

[Agile]

Viessmann boiler are pretty well known about all over the country.

They have a five year warrantee so that should give a good idea of their likely reliability.

Most "plumbers" have little detailed knowledge of boiler workings anyway so I dont see thats very relevant. Viessmann list on their website people who have been to their training days.

WC is in theory fine on UFH but does need the correct control system to power the UFH loops and thats normally that supplied and controlled by the boiler maker.

I dont want to get involved in a detailed long winded discussion ( when Alex is about ) about WC on UFH. Its well covered by many very long threads on this forum. But my reservation is based on UHF having a long thermal time constant which does not fit well when the outside temperature is rapidly changing such as around sunrise and sunset. During the day its fine though. An intelligent predictive system would be required to overcome that though and ideally with an input from the weather forecast.

Tony